The oral cavity of companion animals is composed of both hard tissue such as teeth and soft tissues such as a tongue, gingivae, periodontia, etc. The oral cavity participates in several physical activities, e.g., chewing foods, as well as in chemical activity, i.e., saliva production. Accordingly, the health care for the oral cavity is different from that for the other organs, and sanitary care of the oral cavity is important. For example, dogs and cats are popular companion animals and oral hygiene for them is different from that for human beings since general brushing of teeth of such animals may be very difficult. Therefore, the oral cavity of such animals may often be extremely unsanitary.
In addition, the hydrogen ion concentration or pH value in the oral cavity of dogs and cats is 8.0 or higher so that bacteria such as Escherichia coli and other various putrefying microbes grow in the cavity and make it unsanitary. Putrefying microbes include anaerobic microbes such as Bacteroides, anaerobic Streptococcus, Clostridium, Vaillonella, etc., as well as aerobic bacteria such as Escherichia coli, Pseudomonas aeruginosa, Proteus, and Staphylococcus. Furthermore, food residues adhered to teeth may form plaque containing salivary bacteria. About 70 to 80% of plaque is water, while the remaining content includes proteins. Such proteins are decomposed by putrefying microbes to form offensive substances such as ammonia, hydrogen sulfide, amines, indoles, phenols, mercaptans, etc. The number of salivary bacteria is from 10.sup.7 to 10.sup.11 bacteria per ml of saliva, and includes not only gram-positive bacteria but also various gram-negative bacteria which grow and proliferate in saliva. Microbes in plaque typically include Bacteroides, Gingivalis, Actinobacillus and Actinomycetamcomitans. These gram-negative microbes produce endotoxins that may cause systemic disorders in animals. In addition, they may cause local oral disorders such as halitosis, gingivitis, periodontitis, and often stomatitis, etc., which may be accompanied by pain and pus or loose teeth.
When inorganic salts such as calcium phosphate contained in saliva deposit on plaque, a calcified substance, tartar, is formed. Tartar frequently presses against gingivae and periodontal membranes and causes inflammations of these tissues. Tartar also induces further deposition and accumulation of plaque on teeth, and the resulting toxins and acids from parasitized bacteria may damage or destroy periodontia.
To control periodontitis and plaque in humans both mechanical means such as brushing, scaling and root planing and chemical means such as mouth washing are used. However, since brushing cannot be easily applied in daily home care for companion animals, especially dogs and cats, a chemical means is a preferred method to ensure a hygienic condition in their oral cavity.
The following chemical methods have been used as chemical plaque-controlling agents for companion animals. See for example, "Why carious teeth are formed", Iwanami Shin-sho by S. Hamada, pp. 131-133.
Chlorhexidine Gluconate Solution
An aqueous chlorhexidine gluconate solution has a pH value of from 5.5 to 7.3 and is effective against both gram-positive and gram-negative microbes. However, application of this solution to mucous membranes is not desired because it will yellow the oral cavity and some microbes become resistant to it when used for a long time. In addition, it does not significantly lower the pH value in the oral cavity.
Chlorhexidine Hydrochloride Solution
An aqueous chlorhexidine hydrochloride solution has a pH value of from 5.5 to 7.0 and is also effective against both gram-positive and gram-negative microbes. However, the effects of this solution appear slowly and it does not significantly lower the pH value in the oral cavity.
Iodine Solution
An iodine solution has a pH value of from 5.5 to 6.0 and has anti-microbial activity against gram-positive and gram-negative microbes. However, this solution is not desired because it yellows the area to which it has been applied and, if used for a long period of time, may cause thyroid disorders.
Antibiotics
Antibiotics may be used for both systemic and/or local application to the oral cavity and may exterminate pathogenic bacteria when used to treat periodontitis disorders. However, antibiotics do not remove bacteria or endotoxins that may be firmly adhered to the surfaces of teeth. For local application, use of minocycline hydrochloride is known. However, when antibotics such as minocycline hydrochloride are used for a long period of time, antibiotic resistant microbes may result.
Oral disorders in companion animals such as dogs and cats, such as stomatitis as well as periodontal diseases, gingivitis, marginal periodontitis, and apical periodontitis, typically develop because plaque (a primary cause of such oral disorders) cannot be controlled by daily mechanical means such as brushing of teeth. The present invention provides a composition which disinfects the oral cavity and may be used to prevent or treat oral disorders such as stomatitis, periodontal diseases, gingivitis, marginal periodontitis, apical periodontitis, etc. by chemical means.